FinFETs (Fin Field-Effect Transistors) including pure germanium channels have been developed to increase carrier mobility. However, pure germanium channels may have higher leakage currents than silicon channels due to a larger band-to-band tunneling (BTBT) current in a drain region. A band-to-band tunneling current may be larger in germanium than in silicon because a direct bandgap in germanium is smaller than a direct bandgap in silicon.